Mediastinal lymph node metastasis of lung cancer with an unknown primary lesion having concurrent endocrine abnormality and acanthosis nigricans: report of a case.

We herein describe a patient we encountered in whom mediastinal lymph node metastasis of lung cancer with an unknown primary lesion was complicated by both an endocrine abnormality and acanthosis nigricans. A 66-year-old male visited a local hospital and was diagnosed as having acanthosis nigricans. The patient was referred to our hospital for further examination. Computed tomography scans of the chest and the abdomen showed no adverse findings except for an enlargement of the mediastinal lymph node. No malignant lesions were detected in examinations of the upper gastrointestinal tract. Based on the above findings, the lesion was thus considered to possibly be mediastinal lymph node metastasis of an unknown primary tumor or malignant lymphoma. A thoracoscopic biopsy of the mediastinal lymph node was performed. The patient was diagnosed to have mediastinal lymph node metastasis of lung cancer with an unknown primary lesion and endocrine abnormality resulting from paraneoplastic syndrome. Palliative radiation therapy was initiated to prevent superior vena cava syndrome and esophageal passage failure or dysphagia. The cutaneous lesions markedly improved thereafter. The serum levels of adrenocorticotropic hormone decreased.